The present project on Cell Mediated Hyperacute Rejection (CMHAR) is in it second year of grant support. It concerns a conversion, or modification of rejection pattern of skin grafts by sensitized mice, - an example being the "white grafts". Grafts undergoing CMHAR are characterized by rapid rejection, vascular distrubances, and lack of host cell infiltration. CMHAR is T cell mediated, and part of the proposed research involves a more thorough characterization of the mediating cell(s). Methods to be used are immunoadherence, use of specific antiser, and the development of effector cell clones. One theory to be tested is the "single subset hypothesis" which holds that the conversion of one rejection pattern to the other is a function of the number of effector cells present at the time of placement of test grafts. A search for alternate assay systems ("analogs") is also scheduled, e.g. footpad swelling and migration patterns of effector cells. In the past, "white graft" (and the closely related "red grafts") have been considered analogs of hyperacutely rejected organs. This analogy is limited since hyperacute organ rejection is usually thought of not as cell - but serum mediated. However, a few recent reports indicate that cell mediated mechanisms may well play a role in hyperacute organ rejection, as in CMHAR.